"Lost connection" when debugging with lldb on Mavericks
written on Fri 22 January 2016
Lost connection on simple debugging session
Sometimes you just have to use older system to develop some things. Not because you want to, but simply because you have to.
When trying to use
lldb on Mavericks I had a following problem:
box:default$ ./binary [log] starting binary... [log] it works! box:default$ lldb (lldb) file binary Current executable set to 'binary' (i386). (lldb) proc launch error: process exited with status -1 (lost connection) (lldb)
So, after compiling my own small program, I couldn't launch it in the
debugger. Error code "lost connection" wasn't helping much.
It turns out the solution is easy.
$ sudo /usr/sbin/DevToolsSecurity --enable Password: Developer mode is now enabled.
This might happen if you'll try to use commandline development tools without ever running Xcode, I guess.
This applies also to Sierra, High Sierra, Mojave and probably Catalina as well.
But wait, there's more.
Lost connection on attaching to forked process
lldb isn't a bad debugger, but sometimes it feels like step back from
For example, there's no fork follow mode? Instead of this mode, lldb allows to
attach to a process when it'll be created. You need two terminals; first one
with your debugged program, waiting just before
fork(), and second terminal
with clean and fresh
lldb. Issue this command into the new
lldb session, in
which you'd like to debug your child process:
lldb> process attach --name <name_of_executable_of_your_process> --waitfor
It should wait for your process to fork, and it should start debugging it
(remember about putting some breakpoint before that). In order to make parent
process fork, just step over the
fork() function call in your first
session. The second
lldb should now react.
However, in my case, it only dumped an error:
(lldb) process attach -n testprogram -w error: attach failed: lost connection
In order to fix this case or 'lost connection' error, try issuing this command:
sudo dscl . append /Groups/_developer GroupMembership <your_username>
Now, relogin with
ssh or restart your terminal and try again. For me it
started working flawlessly.
You can also try methods from this post if you're getting other errors, like "unable to attach".